1. Field of the Invention
This invention relates to the field of medical devices using a valve for transferring medication intravenously from one location to another. More specifically, this invention is directed to an improvement in medical valves to ensure that the patient receives the entire dosage of medication, while also providing a means for withdrawing blood from the patient.
2. Background Discussion
The manipulation of fluids for parenteral administration in hospital and medical settings routinely involves the use of connectors for facilitating the movement of fluids between two points. Oftentimes it is desirable to have the patient receive medication from a number of different sources using the same IV. Such a system may be accomplished, for example, by using a Y-connector, a piggy-back connector, a T-connector, or a manifold. Such devices have at least one secondary conduit connected with the primary conduit to add one or more secondary fluids, such as drugs, for example, to the primary fluid being infused into a patient through the primary conduit.
Many connectors or valves, especially those employing several mechanical components, have a relatively high volume of fluid space within them. A serious problem in the medical field has been the existence of this "dead space" at the intersection between the arm and the main bore in medical connectors which prevents the patient from receiving the full dosage of medication, since some of the medicine remains in the dead space of the connector. For example, in several prior art manifolds the operator inserts a syringe into the secondary conduit to introduce a secondary fluid into the primary fluid stream. However, because of the dead space that exists between the end of the syringe and the primary conduit passage, some of the secondary fluid will remain in the junction between the secondary conduit and the primary conduit.
Previous valving devices have focused on removing the undesirable dead space in such devices.
A one-way valving apparatus formed in a manner such that creation of undesirable volumetric dead space is substantially precluded is shown in U.S. Pat. No. 4,666,429 to Stone and U.S. Pat. No. 3,416,567 to Von Dardel et al. In the several embodiments described, a movable element is positioned adjacent to the inner wall of the primary conduit at the junction between the secondary and primary conduits so that the movable element forms a one-way valve. The design of the secondary conduit allows the tip of a syringe nozzle to be substantially adjacent to the movable element. The movable element is partially displaced due to fluid pressure from the flow of secondary fluid through the secondary conduit toward the primary conduit thereby allowing the secondary fluid to pass by the movable element and enter the primary conduit stream. Once the secondary fluid passes through the junction, the movable element returns to its original position, blocking the junction between the primary and secondary conduits.
In the intravenous environment, it is often desirable to utilize a device having the capability of both introducing fluid medication or withdrawing blood from a patient. However, the movable element of the '429 and '567 patents provide only one-way fluid flow, since the movable element is not displaced due to fluid flow in the primary passageway, and therefore, fluid from the patient cannot be drawn into the secondary conduit. Two-way valves are advantageous for drawing a patient's blood back to determine if the IV system is properly inserted into a patient's vein to provide medication. Further, two-way valves have the additional advantage of having the capacity to withdraw blood samples from the patient.
An example of a two-way valve is shown in U.S. Pat. No. 5,269,771 to Thomas, et al. A hollow plunger means is extended through the valve means within a housing to provide free fluid communication between the inlet and the outlet of the device through the central passageway of the plunger means. A syringe coupled to the inlet may then introduce fluid to the patient or, in the alternative, withdraw fluid from the patient.
A serious drawback to this prior art device is the large amount of volumetric dead space that exists not only within the central passageway of the plunger means, but also within the passageways of the housing. Thus, a large amount of the medication to be transferred to the patient remains in the dead space, thereby preventing the delivery of an exact amount of medication. The delivery of an exact amount of medication may be critical in some situations when chemotherapeutic agents are being administered or small children are being treated. An inexpensive medical connector for transferring medication from a number of different sources using the same IV wherein dead space is minimized and fluid in the secondary conduit is bidirectional would be of great benefit to the medical community.